Described below are methods for operating a radio communication system wherein a subscriber station is assigned a first and a second code for the purpose of transmitting messages.
In radio communication systems, messages containing, for example, voice information, image information, video information, SMS (Short Message Service), MMS (Multimedia Messaging Service) or other data are transmitted between a transmitting radio station and a receiving radio station via a radio interface with the aid of electromagnetic waves. Depending on the physical embodiment of the radio communication system, the radio stations in this case can be different types of subscriber radio stations or network-side radio stations such as base stations. In a mobile radio communication system at least some of the subscriber stations are mobile radio stations. The electromagnetic waves are emitted by carrier frequencies that lie in the frequency band provided for the respective system.
Mobile radio communication systems are often embodied as cellular systems, for example conforming to the GSM (Global System for Mobile Communication) or UMTS (Universal Mobile Telecommunications System) standard, having a network infrastructure formed of base stations, devices for monitoring and controlling the base stations and further network-side equipment. Apart from these cellular, hierarchical radio networks organized as wide area (supralocal) networks there are also wireless local networks such as, for example, WLANs (Wireless Local Area Networks) having a radio coverage area that is generally considerably more limited geographically. The cells covered by the radio access points (AP: Access Point) of the WLANs are usually small compared with typical mobile radio cells. Examples of different standards for WLANs are HiperLAN, DECT, IEEE 802.11, Bluetooth and WATM.
Access by subscriber stations to the common transmission medium is controlled in radio communication systems by multiple access (MA) methods/multiplex methods. With these multiple access techniques the transmission medium can be divided up between the subscriber stations in the time domain (Time Division Multiple Access, TDMA), in the frequency domain (Frequency Division Multiple Access, FDMA), in the code domain (Code Division Multiple Access, CDMA) or in the space domain (Space Division Multiple Access, SDMA). Combinations of multiple access methods are also possible.
With code division multiple access methods, subscriber-specific codes are used for communication with subscriber stations, with the result that in the downlink direction the respective subscriber station or, as the case may be, in the uplink direction network-side devices can differentiate the messages to or from the subscriber station from the messages to or from other subscriber stations by establishing a correlation between the received signal and the subscriber-specific code. It is possible for a subscriber station to use a plurality of codes for transmitting messages. In this case the different codes serve to distinguish different transmission channels used by the subscriber station, such as, for example, to distinguish between channels for transmitting payload and signaling information, or to distinguish channels of different services.